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Abstract

Obesity contributes to impaired endothelium-dependent vasodilation (EDV), a precursor to atherosclerotic cardiovascular disease. Women carry a disproportionate burden of cardiovascular morbidity and mortality associated with obesity. Resistance exercise training (RET) is commonly recommended for obesity management, and may improve EDV by increasing the shear stress necessary for nitric oxide production. However, previous studies show that an acute bout of resistance exercise impairs vascular function in sedentary lean adults. We sought to determine if acute resistance exercise impairs EDV in obese women and if 8 weeks of RET protects against this impairment. Ten obese, sedentary young women completed the entire study. Subjects were evaluated at four time points before (weeks 0 and 4), during (week 8), and after (week 12) participation in an 8-week moderate-intensity RET intervention. Brachial artery flow-mediated dilation (FMD) was determined by ultrasound at each time point before and after a single bout of weightlifting (SWL) using a progressive leg-press protocol. Dilation to nitroglycerin (NTG; 0.4 mg), lipids, glucose, blood pressure (BP), waist circumference (WC), body composition, functional capacity, and muscular strength were also assessed at each time point. Brachial artery FMD was reduced after SWL at week 0 (10.5±0.5 to 8.2±0.5%, p=0.002) and week 4 (10.6±0.4 to 8.3±0.5%, p=0.006). At week 8 (after 4 weeks of RET) and week 12 (after 8 weeks of RET) FMD tended to increase after SWL (week 8, 11.2±0.8 to 12.3±0.9, p=0.059 and week 12, 11.1±0.4 to 12.9±1.2, p=0.106) and was significantly greater compared to weeks 0 and 4 (p<0.001). There was no effect of RET on NTG dilation among the time points. However, WC, body composition, functional capacity, and muscular strength were improved but these changes were not related to increases FMD. There were no changes in lipids, glucose, or BP. These data suggest that acute resistance exercise impairs endothelium-dependent vasodilation in obese, sedentary adults and that this impairment is reversible with as little as 4 weeks of resistance exercise training. The results of this study contribute to a better understanding of the mechanisms by which exercise training protects vascular health in obese women.